We continue our development of carbon monoxide (CO)-monitoring technology for laboratory and bedside diagnosis of hemolysis of increased total bilirubin production from other causes. This involves developing and refining instrumentation and techniques for the measurement of excreted CO. These efforts with the cooperation of Natus Medical Inc., San Carlos CA, have resulted in the production of a portable non-invasive instrument for the bed-side monitoring of end-tidal breath CO as an index of bilirubin production for all causes. Recently, high intensity light-emitting diodes (LEDS) have been studied as a possible light for phototherapy of hyperbilirubinemia. These power-efficient, low heat-producing light sources have the potential to deliver high intensity light of narrow wavelength band in the blue-green portion of the visible light spectrum, which overlaps the absorption spectrum of bilirubin.